A mutual savings bank may invest its funds in the water revenue or electric revenue bonds of any incorporated city situated in the United States: PROVIDED, That the city has a population as shown by the last decennial federal census of at least forty-five thousand inhabitants, and the entire revenue of the city's water or electric system less maintenance and operating costs is irrevocably pledged to the payment of the interest and principal of the bonds.
[ 1955 c 13 § 32.20.100. Prior: 1941 c 15 § 8; 1937 c 95 § 6; Rem. Supp. 1941 § 3381-8a.]